This invention relates to automatic performance systems for electronic musical instruments, and more particularly to an automatic performance system for an electronic musical instrument in which performer's operations are stored as digital information signals whereby the digital information signals, or performance information signals, are automatically reproduced with the performance being modified as required.
In general, it is well known in electronic musical instruments, electronic organs for instance, to obtain musical tone signals from harmonic signals containing many high frequency components such as square waves, the electrical circuits being controlled in response to the displacement of movable members such as keys, pedals, levers, push buttons and knobs to generate musical tone information signals or acoustic information signals as desired.
Heretofore, an automatic performance system for an electronic musical instrument has been proposed in which instead of recording acoustic information signals in a tape recorder for instance and reproducing it therefrom, analog performance information signals consisting of harmonic rich tone signals selected by the operations of keys according to the contents of a performance are stored in a proper memory device, and the information signals thus stored are written into the tone coloring circuit or format circuit of the electronic musical instrument thereby to reproduce the performance.
However, in such a conventional automatic performance system for an electronic musical instrument as described above, it is necessary that generated tone signals (analog signals) having a number of harmonic waves which are converted into readily stored signals such as magnetic or optical signals in response to the selective operation of the keys and these signals thus converted are reproduced as the original or initial electrical analog signals. Accordingly, the waveforms of the generated tone signals are liable to be deformed by noises or distortions during the two conversion operations described above, that is, it is difficult to reproduce the performance signals with fidelity. In order to overcome this difficulty, it is necessary to newly modify the circuits including the tone coloring circuit in the following stages, as a result of which the automatic performance system will become more intricate in its construction.
Furthermore, in this conventional automatic performance system, mainly the information on the operation of the keyboard, that is, the information on tonal pitches and tempos is automatically reproduced, but the information on tone color variation, volume variation and effects (vibrato, tremolo and the like) cannot be automatically reproduced, and the movable members such as tone levers and volume knobs must be maintained set at their fixed positions until the reproduction of the information on the keyboard operation mentioned above, or must be readjusted in the reproduction. This is another difficulty accompanying the conventional automatic performance system.
In addition, the conventional automatic performance system necessitates memory devices having a considerably large memory capacity for storing the performance information signals, and it is also difficult to provide proper means suitable for the reduction of the memory capacity.